This invention relates to seating, and in particular to a modular backrest system for wheelchairs.
In general, a wheelchair includes a seat and backrest that are supported by and extend between a pair of side frames, and a pair of wheels attached to the side frames. Backrest posts extend upwardly from the rear end of each frame, and turn rearwardly way from the backrest to form handles that allow a third party to push or move the wheelchair. Collapsible struts are positioned between the frames to maintain the frames in a parallel, spaced apart orientation when the chair is occupied by a user. When the struts are collapsed, the frames move inwardly together to allow for easy transportation or storage of the wheelchair. Typically, the seat and backrest are constructed from flexible material that easily folds when the wheelchair is collapsed.
However, the flexible material of the seat and backrest does not provide optimum support or comfort for the occupant. Contoured universal backrests have been developed to provide improved support for individuals requiring special support, such as those having spinal deformities or muscular atrophy, but these backrests are difficult to adjust to accommodate specific needs and proportions of individual users. Furthermore, the universal backrests are not adjustable for wheelchairs having various widths, and are not readily removable from the wheelchair frame. Special contoured backrests also exist to provide tailored support for a particular user, but such backrests are expensive and cannot be easily adjusted after they are manufactured. For example, molded backrests generally requires at least three stages of fitting: first, the shape and dimensions of the user are obtained; second, a mold is produced based on these dimension; and third, the mold is fit and refined for the particular user. Such custom mold techniques are expensive, labor intensive and time consuming, often taking from two to four months for delivery. Furthermore, the molds must be remade or replaced if the initial fit is incorrect, or if the person's condition or dimensions (height or width) change, or if the backrest no longer properly supports the user. Additionally, such backrests can be heavy and difficult to transport, with full molded systems often weighing up to 25 lbs.
Therefore, it is desirable to develop a backrest system that provides improved support and comfort for wheelchair users. Such a system should be adjustable and expandable to accommodate the unique posture, proportions and support requirements of each individual user. Furthermore, this system should be easy to assemble by a trained technician, and be movable into a multitude of positions, if desired. The system should be adjustable in width to accommodate any of various widths of the wheelchair, and should be able to accommodate wheelchair backrest posts having different diameters. Moreover, the system should be lightweight and easily mounted to and disengaged from the wheelchair to allow for transportation and storage of the chair.